Process of a sensitizing paper with phenolic polymeric material



" United States Patent 3,466,185 PROCESS OF A SENSITIZING PAPER WITH PHENOLIC POLYMERIC MATERIAL John Edwin Gordon Taylor, Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland No Drawing. Filed Mar. 21, 1967, Ser. No. 624,691 Int. Cl. D21h 1/28 US. Cl. 117-361 1 Claim ABSTRACT OF THE DISCLOSURE This invention provides an integral paper sheet sensitized to react with applied solutions of normally colorless chromogenic compounds by exhibiting a subsident stratum of color-reactant phenolic polymeric film material clinging to fibers within said integral paper sheet near its surface but beneath it. This sheet finds an important use as an undersheet in a two-sheet system, the top sheet having a rear surface coated with droplets of printing liquid transferable by pressure to the sensitive undersheet to produce colored marks.

This invention related to a sheet of paper containing therein a substantially undefined subsident stratum of phenolic polymeric film material. More specifically, this invention relates to manufacturing such a sheet by first printing a solution of the polymeric material onto a paper substrate so that the weight of polymeric material ranges from 0.02 pound per ream (dry basis to 0.6 pound per ream (500 sheets of paper 25 inches by 38 inches or 3,300 square feet) and by a subsequent step of applying a solvent for the phenolic polymeric material to said coated in such a manner that the phenolic coating descends in the paper web along the fibers to a depth below the surface of the paper but not through the paper.

This subsident phenolic polymeric material clinging to the fibers provides a product having superior chemical reactive properties with a normally colorless chromogenic compound applied thereto as a liquid from the surface, but said liquid before such application being physically and chemically protected.

While the invention employs the phenolic polymeric film-forming materials for their chemical reactivity, it is obvious that other soluble film-forming chemically reactant materials, whether acidic or basic, fall within the inventive concept.

On Feb. 14, 1967, a United States application for Letters Patent Ser. No. 616,065 was filed by Robert E. Miller and Richard G. Bowler, which application pertained to the coating of phenolic polymeric material onto a paper sheet in limited quantities by use of a Flexographic printing means, which employs resilient roller printing units. A small application of phenolic polymeric material in solution was applied in order that only the nap hairs or fibers of the paper were coated to prevent the formation of a dried continuous varnish-like film which would retard the reaction of the phenolic polymeric material and the applied solutions.

The nap-coated sheet of Miller and Bowler is much superior in response to applied liquids, quantitatively, to the continuously-coated product of heavier coating applications. It has, however, the disadvantage of being sensitive to smudge, because the nap fibers are protuberant above the level of the base structure of the paper sheet and thus vulnerable chemically and physically to applied forces and materials. Also, there was an unexpected loss in the intensity of coloration arising from the transfer to the napcoated sheet of the printing liquid transferred from an overlying sheet. It was assumed that 3,466,185 Patented Sept. 9, 1969 some of the applied liquid was lost into the body of the paper below the nap fibers, where there was no phenolic material to act as an acid.

This invention relates to a process in which the coating on the nap hair of the Miller-Bowler product was subjected to an application of liquid solvent material, which would dissolve the nap hair coating and drive it down into the body of the paper to a determinable distance, depending on the amount of driving-in solvent used.

It was discovered that, upon reducing this concept to practice by the application of the solvent to the alreadynap-hair-coated sheet, the problem of smudge resistance was solved as the nap-hairs were denuded of the polymeric material.

It is believed that this driving down of the metered light coating provided by the Flexographic first applied print by application secondarily of a solvent amounts to an invention which substantially solves the problem of smudge resistance, While at the same time preserving the benefits of a light-weight application of sensitizing material.

Variations in the invention are evident in the use of various film-forming materials, solvents and combinations of solvents. It has been found that the driving of the material down into the sheet did not destroy the intensity of the marks made thereon to any substantial extent and this is thought to be due to the fact that, in the Miller- Bowler sheet in which just the nap hairs are coated, part of the applied liquid color-reactant material flowed into the body of the paper and was useless.

The liquid droplets on the transfer side of an over sheet preferably are retained in minute capsules. Capsulecoated sheet material for use as a transfer sheet liquid reactant supply to make marks on the novel sheet of this invention is disclosed in Us. Patent No. 2,712,507, which issued July 5, 1955, on the application of Barrett K. Green. Earlier, non-capsule, droplet transfer sheets are disclosed in US. Patent No. 2,374,862 which issued May 1, 1945, on the application of Barrett K. Green.

The originally applied nap-coating solution of the polymeric material should be of water-like consistency and when once applied as a coating and the solvent evaporates should leave a nearly undetectable residue, which, though of small amount and weight with. relation to the paper, is extremely effective because of its architectural relationship as an investment on and between the fibers without substantially aifecting the sheet porosity.

A mode of use of this invention is to apply the polymeric material solution by rubber printing plates with an intermediate feeder roll and a supply roll dipping into a tank of the solution and thus applying it into a continuous run of paper, which is then passed over a drying station and wound on a receiving roll. A dried weight of about 0.02 pound of phenolic resin to 0.6 pound per ream of paper specified is adequate for developing marks in an applied solution of 1.5% by weight, crystal violet lactone, which is a basic colorless compound, dissolved in an inert oil to make up an ink.

Therefore, not only is the novel record material efficient in that only a small amount of polymeric material is needed, thus not interfering to any great degree with the normal quality of the paper as to feel and as to its ability to be printed with ink in the ordinary way, but it is present in its most efficient form as far as area per square unit of paper is concerned, and gives more-thanadequate provision for the making of an intensely colored mark with the least amount of applied fluid equivalent-to or better-than-now-known for ordinary color-reaction types of printing sheets.

The invention having been described with reference to just the presence of phenolic type of polymeric material thereon, it is to be understood that it is within the scope of the invention to add other materials to the coating to take advantage of its novel construction.

Among the phenolic polymers found useful are paraphenylphenol polymers, paraphenylphenol-formaldehyde polymers, paraalkylphenol-formaldehyde polymers, parahalophenol-formaldehyde polymers, paranitrophenolformaldehyde and alkyl-phenol-acetylene polymers, which are soluble in common organic solvents and possess permanent fusibility in the absence of being treated by crosslinking materials. A specific group of useful phenol-aldehyde polymers are members of the type commonly referred to as novolacs (as sold by Union Carbide Corp., New York, NY.) which are characterized by solubility in common organic solvents and which are, in the absence of cross-linking agents, permanently fusible. Generally, the phenolic polymer material-found useful in practicing this invention is characterized by the presence of free hydroxyl groups and the absence of groups such as methylol, which tend to promote inf usibility or crosslinking of the polymer, and by their solubility in organic solvents and relative insolubility in aqueous media. Again, obviously, mixtures of these phenolic polymers can be employed.

A laboratory method useful in the selection of suitable phenolic polymeric materials is the determination of the infra-red absorption pattern of a candidate material.

t has been found that phenolic polymeric materials showing an absorption in the 3200 3500 cm." region (which is indicative of the free hydroxyl groups) and not having an absorption in the 16001700 cm? region are suitable. The latter absorption region is indicative of the desensitization of the hydroxyl groups and, consequently, makes such groups unavailable for reaction with the chromogenic materials.

The preparation of phenolic formaldehyde polymeric materials for practicing this invention is described in Industrial and Engineering Chemistry, volume 43, pp. 134 to 141, January 1951, and a particular polymer thereof is described in Example 1 of United States Patent No. 2,052,093, issued to Herbert Honel on Aug. 25, 1936, and the preparation of the phenol-acetylene polymers is described in Industrial and Engineering Chemistry, volume 41, pp. 73 to 77, January 1949.

Solvents for these phenolic materials are ordinary organic solvent materials of relatively great volatility and of low toxicity, among which are the following: normal butanol, ethanol, toluene, xylene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol diacetate, ethylene glycol dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol monoacetate, ethylene glycol monobenzyl ether, ethylene glycol monobutyl ether (2-butoxyethanol), ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monophenyl ether, and ethyl acetate.

An example of this invention consisted of dissolving 15% by weight of specified phenolic polymeric material in a mixture of 25%, by weight, of ethanol and 75%, by weight, of ethyl acetate. The above formulation can be printed onto a paper substrate by means of a Flexographic printer equipped with several printing stations so that the sequential coatings, first with the phenolic material, and then with a solvent mixture to carry the phenolic material into the sheet, can be effected on a single advance of a paper web through the press.

The second coating (solvent) was composed of equal moieties of ethyl acetate and ethylene glycol monoethyl ether. The finished product exhibited an enhanced resistance to smudging when reacted with crystal violet lactone solution to form a colored mark. It is to be noted that the solvent used in the second coating is not the same as that used as the solvent part of the first coating. This was done to illustrate the freedom of choice as to solvents.

4 With a particular paper substrate, solvents individually or as mixtures will have different effects as to penetration, solvent power, vaporization, and incompatibility, and with this in mind the practitioner has a wide latitude of choice to achieve the desired results in depth of penetration and porosity thereof with a given fiber structure.

Other solvents eligible are ethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol monoacetate, ethylene glycol monomethyl ether acetate, and ethylene glycol monophenyl ether and mixtures of these solvents.

One mode of applying the second coating (solvent) is to apply it by rubber printing plates with an intermediate feeder roll and a supply roll dipping into a tank of the solvent, or solvent mixture, onto a continuous run of paper which is then passed over a drying station and wound on a receiving roll. Approximately .1 pound to 2 pounds of solvent per ream of paper 25 by 38 inches by 5000 sheets is adequate for practicing the application of the second coating.

It is to be understood that the solvents described above are assigned for use in applying the phenolic material and are not necessarily for use as a solvent vehicle to facilitate reactive contact between color-forming components. In the latter instance, the liquid solvent must be capable of dissolving both of the mark-forming components. The solvent chosen should be capable of dissolving at least 0.3% on a weight basis, of the chromogenic material, and at the same time a corresponding amount of polymeric material to form an etficient reaction. However, in the preferred system, the solvent should be capable of dissolving an excess of the polymeric material, so as to provide every opportunity for utilization of all of the chromogenic material present and, thus, to assure the maximum coloration at a reaction site, with the least amount of the expensive chromogenic material.

Among the modes of application of the coating liquids that can be used are roller-coating spraying, knife, spreader-bar or blade coating, brushing, or any other mode of application by which controlled amounts can be applied.

What is claimed is:

1. A process of impregnating a sheet of paper with a substituent stratum of phenolic polymeric material to sensitize it with a reactant of acidic properties to develop color in an applied colorless base color reactant comprising (A) printing a solution of organic solvent-soluble phenolic polymeric material onto a face of a paper substrate that when dried leaves a film of the polymeric material in an amount of from 0.02 to 0.6 pound per ream of paper 24 by 36 inches by 500 sheets that festoons the protuberant fibers of said paper sheet,

(B) drying said solution in situ,

(C) applying at least one solvent for the polymeric material into said face of said paper substrate so that a solution is formed of said polymeric material which solution moves into said paper to a level below said face, and

(D) drying said solvent applied in step C to leave the polymeric material on the fibers within the sheet without occluding the pores.

References Cited UNITED STATES PATENTS 2,757,085 7/1'956 Paquin 1l736.2 3,244,548 4/ 1966 Sullivan 11736.2

FOREIGN PATENTS 428,386 5/ 1935 Great Britain.

MURRAY KATZ, Primary Examiner U.S. c1. X.R. 1. .-36.8. 1 63 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent -No. 3,466,185 September 9, 1969 John Edwin Gordon Taylor It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 25, "related" should read relates line 32, "basis" should read basis) line 36, after coated" insert paper line 56, after "polymeric" insert film Column 4, line 44, "substituent" should read subsident line 56, "into" should read onto Signed and sealed this 15th day of September 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, IR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

